1. Field of the Invention
This invention relates to the field of testing fired ink from inkjet pens for purposes of analyzing the components of the ink to determine whether an inkjet pen is performing properly.
2. Description of the Related Art
Inkjet pens are widely utilized in printing systems, and are increasingly finding uses in other applications to provide controlled delivery of a wide range of substances. For many reasons, it is advantageous to analyze the actual output from an inkjet pen. However, many quantifiable parameters such as solvent concentrations and thermal degradation products of the ink/printhead interaction are difficult to analyze with traditional gas chromatography injection and mass spectrometry methods due to their volatility and the necessity of producing large quantities of analyte; large analyte quantities are needed due to the inefficiency of traditional sample introduction (i.e., liquid injection).
The current method for analysis of fired ink requires that the pen be fired onto a reasonably clean glass fiber pad; the pad is usually held under the printhead in a Drop Break-off Observation System (xe2x80x9cDBOSxe2x80x9d) (i.e., an optical system having a camera pointed at an inkjet pen which allows an analyst to see the way in which ink drops are formed on a substrate upon being fired by the inkjet pen). Following the firing of the ink onto the glass fiber pad, the current method uses a thermal desorption inlet system coupled to a standard gas chromatograph/mass spectrometer; the gas chromatograph/mass spectrometer analyzes the volatile components of the ink which are released from the glass fiber pads.
After the ink is fired onto the glass fiber pad: (a) the pad is cut to an appropriate size and placed inside a thermal desorption tube which, in turn, is placed within a thermal desorption inlet coupled to a gas chromatograph/mass spectrometer; (b) the inlet to the gas chromatograph/mass spectrometer is closed (i.e., sealed); (c) the carrier gas flow in the gas chromatograph/mass spectrometer is restored; and (d) the inlet zone is heated to an appropriate temperature to achieve thermal desorption. The analyte (i.e., the ink to be analyzed) is mixed with the carrier gas and is swept onto the analytical column where it is cryo-focussed by cooling the gas chromatograph/mass spectrometer oven with a jet of liquid nitrogen. When the analyst determines that the sample has been sufficiently desorbed, the oven temperature is brought to an operating temperature (usually approximately 50xc2x0 C.) and the analysis begins.
Unfortunately, the traditional analytical method has a plurality of inherent drawbacks which: (a) reduce the integrity of the ink to be analyzed (either by loss of volatile components or by contamination); (b) create an undesirably long analysis duration; (c) require great precision and care when managing the glass pads and depositing the ink thereon; and (d) cause chromatographic peak broadening due to analyte trickling into the column while the analysis is being completed (thereby reducing the benefit cryo-focusing would otherwise generate). These drawbacks are discussed in more detail hereafter.
First, although glass fiber pads are a better substrate than most available materials for thermal desorption, they are not ideal in several respects. For instance, the current method contemplates depositing the ink onto the glass fiber pads at ambient temperatures at which loss of volatile ink components can occur. Moreover, critical amounts of volatile ink components may further be lost when: (a) the glass fiber pads are transferred into the thermal desorption tube associated the gas chromatograph/mass spectrometer; and (b) when the thermal desorption tube is transferred into the gas chromatograph/mass spectrometer. The lost of volatile ink components when the ink is deposited on the glass fiber pads (due to the ambient temperatures at which such transfer occurs) and when the pads are subsequently moved into the desorption tube and then into the gas chromatograph/mass spectrometer can greatly reduce the integrity of the chromatography. In addition, although glass fiber pads are the most suitable substrate for the performance of this traditional method, the pads are known to contribute contaminants to the ink deposited thereon thereby further degrading the integrity of the chromatography.
Glass fiber pads are also problematic for a host of additional reasons. First, by way of example, glass fiber pads must be handled with great care to avoid sample contamination with finger oil, etc. Second, as the analyte ink is only fired onto a portion of the pad, an analyst must choose the area to be analyzed very carefully. Third, the system by which the ink is deposited is particularly inconvenient as the analyst must place the pad precisely, by hand, in the DBOS machine. Fourth, in terms of obtaining accurate analysis results, the analyst must assume that the glass fiber pads (which are not chemically deactivated) do not change the chemical composition of the analyte ink when heated in the inlet liner.
The traditional process itself also suffers from inherent drawbacks. For example, constantly opening and closing the gas chromatograph/mass spectrometer is cumbersome and very time consuming. If one waits until the heated zone in the inlet has cooled to room temperature, each complete analysis can easily take more than an hour and half, thereby severely limiting sample throughput. Unfortunately, it is prudent to cool the inlet in this way to avoid sample oxidation when the inlet liner and sample (and an unavoidable amount of outside air) are introduced into a hot inlet.
Cryo-focusing is traditionally used to avoid introducing the sample into the column over a long period of time, which would broaden analyte chromatographic peaks unacceptably (as the principal advantage of modern capillary column gas chromatography is the superior resolution of sample components in sharp peaks); this advantage is destroyed if the sample mixture is allowed to seep into the instrument over time. By concentrating all of the components of interest in a single, short section of column (which can be easily heated by the gas chromatograph oven), cryo-focusing allows the analyst to start the analysis of the entire sample at once. Unfortunately, in practice, it is possible that the entire sample to be analyzed will not be transferred to the cryogenically cooled analyte column before the analysis is started. As a result, small amounts of less volatile components will continue to trickle into the system during the run and will, thereby, contribute to high background response (i.e., chromatographic peak broadening) and generally poor chromatography. Although this peak broadening is a problem with standard gas chromatographs, it is particularly noticeable in gas chromatograph/mass spectrometers. In addition, such poor chromatography is difficult to avoid using the traditional method as the sample can not be removed from the heated zone until the analysis is complete.
Accordingly, there is a need for an improved method for determining the volatile components of inkjet ink from a complete and functional inkjet pen. In determining the components, the purity and quantity of the sample to be analyzed may be improved by eliminating, or at least reducing one or more of: (a) the amount of contaminants that are added to a sample of inkjet ink to be analyzed; and (b) the amount of volatile ink components lost prior to analysis. In addition, there is a need for an apparatus capable of performing a method having one or more of the aforementioned benefits which is both easy to use and which shortens the duration required for traditional analysis.
A first embodiment of the invention herein described addresses a gas chromatography inlet system. The inlet system includes a block having a chamber therein accessible through an opening in a side of said block. In addition, the system includes a stage, located in the chamber, which is adapted to receive an analyte sample. The system also contains a temperature adjusting mechanism which is adapted to alter the temperature of the block and stage. A cover is included and is adapted to close the opening in the block. The block has an inlet and an outlet; whereas the inlet is adapted to receive a transfer gas and direct it over the stage, the outlet is adapted to transmit the transfer gas. When the cover closes the opening, the chamber is inaccessible from an exterior of said block except via the inlet and outlet. Further, when the stage is heated by the temperature adjusting mechanism, the apparatus will be capable of vaporizing at least a portion of an analyte sample deposited on the stage.
The temperature adjusting mechanism of this first embodiment of the invention may include a flow of liquid nitrogen. Moreover, if liquid nitrogen is used, it may be used to cool the block and the stage therein before the analyte sample is deposited on the stage. Finally, the stage in the first embodiment may be, and preferably is, glass.
A second embodiment of the invention herein described addresses an analytical apparatus. The analytical apparatus of the second embodiment is similar to the aforementioned first embodiment, however, unlike the previously described first embodiment apparatus, the second embodiment analytical apparatus includes an analytical device. More specifically, the second embodiment apparatus includes a block containing a heating element and having a chamber therein; the chamber is accessible through an opening in a side of said block. A cover is included which is adapted to close the opening in the block. In addition, the apparatus includes a stage, positioned in the chamber, which is adapted to receive an analyte sample. An inlet in the block is adapted to receive a continuous flow of transfer gas and is adapted to direct the continuous flow of the transfer gas over the stage. In addition, an outlet in the block is adapted to receive the transfer gas. The second embodiment also includes an analytical device (as previously mentioned) which is in fluid communication with the outlet. In this second embodiment, when the cover closes the opening, the chamber is inaccessible from an exterior of the block except via the inlet and outlet. In addition, the analytical device is adapted to receive the transfer gas and to determine the components of the analyte sample as supplied thereto in by the transfer gas.
In the second embodiment, the analytical device can be a variety of devices including a gas chromatograph, a mass spectrometer, or a combination gas chromatograph/mass spectrometer. It is also contemplated that the second embodiment may include a temperature adjusting mechanism which is adapted to alter the temperature of the block. If such a temperature adjusting mechanism is included, it could involve a flow of liquid nitrogen.
The second embodiment may also include an intake line, an exhaust line, or both. If the second embodiment includes a temperature adjusting mechanism, it may vaporize an analyte sample deposited on the stage thereby creating an analyte sample vapor which can mix with the transfer gas. Moreover, if an intake line is provided, it can be adapted to transmit a mixture of the transfer gas and the vaporized analyte sample from the block to an inlet in the analytical device. Similarly, if an exhaust line is provided, it can be adapted to transmit a mixture of the transfer gas and the vaporized analyte sample from the block to an exterior of the apparatus.
If the second embodiment includes an intake line and an exhaust line, valves may be positioned in those lines. A first valve may be adapted to prevent the mixture of the transfer gas and the vaporized analyte sample from flowing through the intake line. Moreover, a second valve may be adapted to prevent the mixture of the transfer gas and the vaporized analyte sample from flowing through the exhaust line. It is also conceivable that one connector valve can serve as both the first and the second valves.
The invention described herein also addresses both a method of determining the components in an ink fired from an inkjet pen as well as a method for determining whether an inkjet pen is performing properly. With respect to the method of determining the components in an ink fired from an inkjet pen, the method includes: (a) cooling a block having a stage in a chamber therein; (b) depositing an analyte sample of the ink onto the stage; (c) sealing the chamber; (d) heating the stage to vaporize at least a portion of the analyte sample thereon; (e) passing a transfer gas over the stage so that the vaporized portion of the analyte sample is mixed with the transfer gas forming a gaseous mixture; (f) receiving the gaseous mixture in an analytical device which is in fluid communication with the block; and (g) determining, by means of the analytical device, the components of the gaseous mixture and thereby the components of the vaporized portion of the analyte sample.
In determining the components in an ink fired from an inkjet pen, the analytical device can be any number of devices including a gas chromatograph, a mass spectrometer, or a combination gas chromatograph/mass spectrometer. If a gas chromatograph/mass spectrometer is used as the analytical device, the method may include concentrating the gaseous mixture in the gas chromatograph/mass spectrometer, prior to the step of determining the components of the gaseous mixture (and thereby the components of the vaporized portion of the analyte sample).
In addition, the chamber in the block used in performing the method may have an opening therein. If such an opening is provided, the step of sealing the chamber may include covering the opening with a cover and establishing an airtight closure between the cover and the opening by means of a seal. The step of cooling the block may include passing liquid nitrogen over the block. The method may include, after the steps of cooling of the block and depositing the analyte sample of the ink onto the stage, cyro-focusing the analyte sample on the stage. In addition, the method may also include, prior to the step of cooling the block, heating the stage to remove contaminants thereon.
To ensure that the components of the analyte sample are determined as accurately as possible, it is preferable that the transfer gas be a gas which does not chemically react with the analyte sample; such a non-reactive transfer gas could be helium. Moreover, in determining the components of the analyte sample, the method may include determining the relative amounts of the components in the vaporized portion of the analyte sample.
After a sufficient amount of the gaseous mixture is received in the analytical device, the method of determining the components of the analyte sample may include closing a valve in an intake vessel which carries the gaseous mixture from the chamber to the analytical device; closing the valve in this fashion would prevent additional gaseous mixture from entering the analytical device. If the valve in the intake line is closed, the method may further include opening a valve in an exhaust vessel into which the additional gaseous mixture may flow. Finally, the method may contemplate closing a valve in a transfer gas supply vessel which supplies the transfer gas to the chamber thereby preventing subsequent transfer gas from entering the chamber.
As previously mentioned, the invention also addresses a method for determining whether an inkjet pen is performing properly. This method includes: (a) depositing an analyte sample of ink from an inkjet pen onto a stage in a chamber in a block; (b) heating the stage to vaporize at least a portion of the analyte sample thereon; (c) passing a transfer gas over the stage so that the vaporized portion of the analyte sample is mixed with the transfer gas forming a gaseous mixture; (d) receiving the gaseous mixture in an analytical device which is in fluid communication with the block; (e) determining, by means of the analytical device, the components of the gaseous mixture and thereby the components of the vaporized portion of the analyte sample; and (f) determining, based on the components of the vaporized portion of the analyte sample, whether the inkjet pen is performing properly.
In performing this method for determining whether an inkjet pen is performing properly, the analytical device can be any number of devices including a gas chromatograph, a mass spectrometer, or a combination gas chromatograph/mass spectrometer. In addition, the inkjet pen may comprise a plurality of resistors and/or a plurality of firing chambers. If the inkjet pen comprises a plurality of resistors, the method may include diagnosing improper firing by at least one of the resistors. Similarly, if the inkjet pen comprises a plurality of firing chambers, the method may include diagnosing failures in at least one of the firing chambers.
A structural understanding of the aforementioned gas chromatography/mass spectrometry inlet system and the analytical apparatus, as well as the methods of using the inlet system and the analytical apparatus (to determine inkjet components and whether an inkjet pen is functioning properly), will be easier to appreciate when considering the detailed description in light of the figures hereafter described.